Is it correct that Brahms and Hanslick as conservative forces, following the classical line of the romantics as opposed to Liszt and his high romantical ideals, critized Liszt? What did they critize? Did they find Liszts music shallow? Mere empty display? Were they critical against his transformation technique of themes as opposed to using classical forms?
Please help 
He did, indeed, fall asleep, and many biographers consider it to be an act of profound rudeness. Prior to Lizst playing his sonata, Liszt had asked Brahms to play his own E-flat minor Scherzo. Brahms declined. Why? Some believe he was intimidated to play before Liszt. Some say he was simply a very nervous performer. But, decline he did. So, Liszt took the barely readable manuscript from him and sight read the piece flawlessly, complete with an admiring, running commentary. He praised Brahms to the skies.
But, fundamentally, Brahms detested Liszt's music and the movement he founded for "Music of the Future." Essentially, music that went beyond formal structures and included programmatic elements and, for Brahms, an excess of emotion, most of which Brahms found to be just plain histrionic.
In one view, yes, Brahms could be seen as a "conservative" reacting against Liszt and Wagner's "radicalism." But I think that is too simplistic. Regarding Liszt's music, well, yes, Brahms found it shallow, overwrought and excessive. He regarded Wagner, however, quite highly.
Topic: Brahms falling asleep during Liszt performance?